Geoff Freed (WGBH) and I review the section dealing with multimedia as part
of a different task. below are some comments/thoughts/explanations.
from http://www.w3.org/TR/1999/WAI-USERAGENT-19990331/
Guideline 5.2 Ensure user control over alternative representations of
content
User agents must give users access to author-supplied alternative
representations of content (descriptions of images, captions for video or
audio, etc.) since some users cannot perceive the primary content due to a
disability or a technological limitation (e.g., browser configured not to
display images). See also guideline 5.3.
General checkpoints:
5.2.1 [PriorityÂ 1]
Ensure that the user has access to alternative representations of content
(e.g., the value of "alt" in HTML or SMIL
<note>there is no "alt" in SMIL, perhaps "captions or audio description in
SMIL"</note>,
the resource designated by "longdesc", or the content of OBJECT in HTML 4.0,
the "summary" attribute for tables in HTML, etc.).
<new>Checkpoints for images: </new>
<note>these two checkpoints seem to deal specifically with images, so we
grouped them together, as well as changed/inserted the groupings of other
media types.</note>
5.2.2 [PriorityÂ 2]
When no alternative text representation has been specified, indicate what
type of object is present.
<note>possible technique-indicate what alternatives are available from the
source in SMIL player</note>
5.2.3 [PriorityÂ 3]
When alternative text has been specified explicitly as empty (i.e., an empty
string), render nothing.
<new> Checkpoints for Multimedia:
Multimedia includes audio and video information with specific alternative
representation of information. Alternative representations of audio includes
other audio language tracks and captions (also in other languages).
Alternative representations of video include other audio language tracks,
captions and audio description.
Checkpoints for captions: </new>
<note>We thought it made sense to have specific checkpoints for captions.
They are text representations of audio information. Alternative audio
representations (other audio languages) are found in the Checkpoints for
audio section. A person from the A/V field would categorize the information
in this manner. </note>
<note>Moved from checkpoints for audio</note>
5.2.5 [PriorityÂ 2]
Allow the user to specify that captions for audio be rendered at the same
time as the audio.
<note> separated captions from audio description and made 2 separate
checkpoints. Audio description is alternative content for video and should
be included in that section (see 5.2.9).</note>
<note>Moved from checkpoints for video</note>
5.2.6 [PriorityÂ 1]
If a technology allows for more than one caption track (e.g., text,
alternative language (subtitle), etc.), allow the user to choose from among
tracks.
<note> separated captions from audio description and made 2 separate
checkpoints. Audio description is alternative content for video and should
be included in that section (see 5.2.9a).</note>
Checkpoints for audio:
<note>Moved from checkpoints for video</note>
5.2.7 [PriorityÂ 1]
If a technology allows for more than one audio track (alternative language
or overdub) for video, allow the user to choose from among tracks.
Checkpoints for video:
5.2.9 [PriorityÂ 1]
Allow the user to specify that audio descriptions for video be rendered at
the same time as the video.
<note>separated the captions, see 5.2.5</note>
<new>
5.2.9a [PriorityÂ 1]
If a technology allows for more than one audio description track for video,
allow the user to choose from among tracks.</new>
<note>mirroring caption checkpoints</note>
<new>5.2.x [PriorityÂ 2]
Allow the user to specify that sign language video track (if available) be
rendered at the same time as the video. </new>
<note>this was not specified before. it is possible with in the SMIL spec to
provide this capability</note>
Jim Allan, Statewide Technical Support Specialist
Texas School for the Blind and Visually Impaired
1100 W. 45th St., Austin, Texas 78756
voice 512.206.9315 fax: 512.206.9453 http://www.tsbvi.edu/
"We shape our tools and thereafter our tools shape us." McLuhan, 1964